Field of the Invention
This invention relates to seismic exploration, and more particularly, to a method and apparatus for transmitting seismic energy directly into the earth or sea floor underlying a body of water.
Poor quality seismic data is often acquired offshore in what is referred to as the transition zone. That zone is an area of nearshore submerged lands, e.g., the coastline out to water depths of approximately sixty feet. The probability of obtaining quality seismic data is worsened when a layer of ice covers the body of water in the transition zone.
Various attempts have been made to reduce the noises that mask the desired seismic signals in gathering seismic data in transition zones. Unfortunately, attempts to attenuate the water column and the ice flexural wave effects have been only partially successful.
The present invention is an alternative energy source for gathering seismic data in the nearshore areas and, particularly, in such areas of the Arctic during the winter. This invention is unique in its ability to eliminate the source generated noise related to the water and any ice layer by lowering the energy source through the water and below the ice layer and coupling the source directly to the sea floor.